It is often desirable to have a means of effecting an adjustment between surfaces while also being able to lock the surfaces into the adjusted position. It is known to accomplish this result by use of matching serrations on the two members. To make an adjustment, the surfaces are separated, moved with relation to each other, brought together again, and the parts fastened in place. If rotational movement is desired, the serrations extend radially; if reciprocal movement is desired, the serrations extend parallel to each other. When bi-directional adjustment is required, it is known to use three members instead of two. The middle member has serrations on one side extending parallel to each other and serrations on the other side extending normal to the first serrations. The outside members are serrated to match the side of the middle member being contacted. In U.S. Pat. No. 2,685,469, bi-directional adjustment was obtained by use of matching parallel serrations over a limited area of the surfaces, matching parallel serrations normal to the first serrations over a different limited area of the surfaces with clearance between the surfaces outside the serrated areas. It was found that bi-directional adjusting lightweight couplings would be obtained by use of a multiplicity of projections with matching recesses.